Spain's Dani Pedrosa has led from the start to win the San Marino MotoGP Grand Prix on another sad day for the sport after Japanese rider Shoya Tomizawa died following a crash in an earlier race.

Honda rider Pedrosa, second in the overall standings, finished ahead of championship leader and compatriot Jorge Lorenzo of Yamaha to cut the gap at the top to 63 points with six races remaining this season.

Tomizawa died in hospital after suffering a shocking crash in the earlier Moto2 race when he was hit by two other bikes.

Pedrosa was in no mood to celebrate his victory.

"Now my head is away from the race. There are no words," he told Mediaset television.

"For the race everything was perfect, but now I'm totally shocked."

A 13-year-old also died in a minor race before the Indianapolis MotoGP Grand Prix in the dangerous sport's last outing in August.

Pedrosa kept pulling away from Lorenzo from the start and the outcome of the race was never in doubt.

World champion Valentino Rossi came in third on his Yamaha, having overtaken Australia's Casey Stoner three times during an engaging duel in the middle of the race.

Stoner, who will be replaced by Rossi at Ducati next year, slipped further back and finished fifth behind Andrea Dovizioso.